Description of Third Cousins
People who share the same great-great-grandparents, are not first cousins, and are not second cousins, are defined as third cousins. In other words, they are the children of second cousins. See our Third Cousins illustration below:
John and Mary are third cousins, because they are not siblings, they are not first cousins, they are not second cousins, but they share great-great-grandparents.
Did you know that both the second and the third Presidents of the United States were married to their third cousin?
President John Adams was married to his third cousin Abigail Smith and President Thomas Jefferson was married to his third cousin Martha Wayles.
Learn more about the First Ladies.